The function of the kidneys is to maintain normal ionic concentrations in the blood. Normally the kidneys maintain the blood ionic composition within very tight range and imbalance produces very serious health consequences including death. The goal of this grant is to understand the ion channels that function in the kidney to transport chloride and maintain chloride homeostasis in the body. This application will focus on an exciting new family of chloride channels that was just discovered, the anoctamins (also called TMEM16). We have preliminary data that several anoctamins are expressed in kidney and are likely to play important roles in chloride secretion and/or absorption. This application will investigate the expression of anotamins in normal mouse and human kidney and in kidney from human and from mouse models of polycystic kidney disease. Expression will be determined using quantitative RT-PCR, western blot, and immunofluorescent confocal microscopy. The functional structure and organization of the anoctamin channel will be investigated using electrophysiological (whole-cell and single channel patch clamp recording) and biochemical analysis of cells expressing Ano1. The location of Ca2+ binding sites and mechanisms of regulation of Ano1 by voltage and Ca2+ will be explored to develop a quantitative model of how anoctamin channels are gated.